1. Field of the Disclosure
This disclosure generally relates to a portable electronic device and, more particularly, to a portable electronic device and a rotation detection method capable of detecting the rotation direction when the tilt angle is ±90 degrees.
2. Description of the Related Art
Just as its name implies, a portable electronic device is portable for users, and it also has the merit that a displaying direction of a display device thereof is changeable according to the usage requirement.
For example, referring to FIG. 1A, it shows a portable electronic device rotated with a rotation angle equal to 0 degree and a displaying state of its display device, wherein the display device takes the X′-axis as a vertical axis and the Y′-axis as a horizontal axis for displaying an image. When the portable electronic device is rotated clockwise by 90 degrees as shown in FIG. 1B, the display device changes the Y′-axis as the vertical axis and changes the X′-axis as the horizontal axis for displaying in order to make the displayed image easier to be observed by a user. Accordingly, the user may select a suitable displaying direction to operate the portable electronic device when operating different applications thereby improving the user experience.
However, limited by the detection limitation of an acceleration sensor, the conventional portable electronic device is not able to correctly detect the rotation angle in all conditions. For example, when a display surface of the portable electronic device is parallel to the horizontal plane, i.e. the portable electronic device being put on a table surface or operated by the user in a lying position, as three detection axes of the acceleration sensor 9 (e.g. X, Y and Z) are coincident with three dimensional axes of the conventional portable electronic device (e.g. X′, Y′ and Z′), as shown in FIGS. 2A and 2B, the acceleration sensor 9 is unable to effectively detect the rotation angle when the Z-axis detection direction thereof is perpendicular to the horizontal plane such that the displayed image by the display device can not be changed according to the rotation of the portable electronic device by the user.